1. Field of the Invention
The present invention relates to an optical disc apparatus, and more particularly to a recordable optical disc apparatus such as a DVD-R/RW drive.
2. Description of the Related Art
In an optical disc apparatus, data is recorded while optimizing recording power through technology designated as OPC (Optimum Power Control) and ROPC (Running Optimum Power Control). Under OPC, prior to actual data recording, test data is recorded on a predetermined area (PCA: Power Calibration Area) of an optical disc while variously changing levels of recording power and the recorded test data is reproduced to select a recording power, with which reproduction signal quality (for example, β value) of the reproduced test data becomes ideal, as the optimum recording power. On the other hand, under ROPC, considering that recording film sensitivity of the optical disc is not always uniform in a plane, the amount of light returned during data recording is monitored to carry out feedback control of recording power so as to keep the amount of returned light constant when data is actually recorded under the optimum recording power determined by OPC. The amount of returned light, typically used, is the amount of light at level B, which is obtained when a pit is formed by irradiation of recording power (that is, the amount of returned light diffracted from the pit). More specifically, when the amount of returned light at level B is smaller than a fixed value, the recording power is reduced based on the determination that an excessive number of pits are formed. On the contrary, when the amount of returned light at level B is larger than the fixed value, the recording power is increased based on the determination that an adequate number of pits are not formed.
When data is recorded on an optical disc of a CD-R/RW or the like, data with pit lengths of 3T to 11T is recorded. Because it is difficult to monitor the amount of returned light in order to carry out the feedback control when the pit length is short, ROPC is carried out by detecting the amount of light returned while the longest 11T is recorded. The CD-R/RW has a standard that 11T is contained in synchronous information (SYNC) and always appears twice in a row. Because either one of the two consecutive 11T's always becomes a mark (a segment where a pit is formed by irradiation of recording power), due to the standard, it is possible to carry out ROPC using 11T at regular intervals (in other words, at the same timing as the periodically inserted synchronous information) so as to optimize the recording power at regular intervals.
For DVD-R/RW, although the pit lengths of 3T to 11T are formed just as with the CD-R or the like, there is a different standard where 14T is used as synchronous information and is not inserted twice in a row (as a pair of the mark and the space), as is the case with the CD-R, but is inserted only once. Further, in the standard, it is not specified whether 14T becomes the mark or the space. When every 14T is the space, for example, it is not possible to execute ROPC because the pit is not formed by the longest 14T, with a result that it becomes difficult to maintain recording quality due to inability to optimize the recording power at regular intervals. In order to allow ROPC to be executed, every 14T may be assigned to a mark. However, in this case where every 14T is a mark, there is a possibility that low-frequency components are increased due to the increased DSV.